1. Field of the Invention
The present invention relates to a paper additive composition that can provide bulky and soft paper having a sufficient strength and a method for producing paper using the same.
2. Description of the Related Art
In recent years, in view of shortage of pulp resources and a consequent increase in the price of pulp, effective utilization of the resources and environment protection, it has been attempted to reuse waste paper pulp, reduce the amount of pulp used for paper production, and reduce the basis weight of various paper products. In addition, in order to reduce the production cost of paper product or increase the production amount, and further to prevent accidents such as the toppling over of vehicles or the falling of the load due to overloading when paper products are being transported, it is very important to reduce the basis weight of paper to make it light. However, for thin paper whose basis weight is reduced or paper containing a large amount of waste paper pulp, the bulkiness is insufficient, and printed ink penetrates the paper to the back face. For these reasons, there is a demand for a method for producing bulky paper even when the amount of pulp is small or when a large amount of waste paper pulp is contained.
The following methods are disclosed as methods that provide bulky paper: a method that employs an additive comprising a polyoxyalkylene adduct of a fatty acid or a polyoxyalkylene adduct of a fatty acid ester in Japanese Laid-Open Patent Publication (Tokkai) No. 11-200284; a method that employs an additive containing oils or fats or a nonionic surfactant derived form sugar alcohol in Japanese Laid-Open Patent Publication (Tokkai) No. 11-200283; and a method that employs a cationic compound, amine or its salt, an amphoteric compound, a nonionic surfactant or the like as an additive in Japanese Laid-Open Patent Publication (Tokkai) No. 11-269799. However, these methods failed to provide a sufficient bulkiness effect, and the strength of the resultant paper is also insufficient. In order to increase the strength of paper, a method of adding a polymer compound such as starch, polyacrylamide, or polyamidepolyamine-epichlorohydrin resin is known. However, when the above-described additives for providing bulky paper and the polymer compound are used together in a paper formation system, the bulkiness effect of the additive is reduced.
Japanese Laid-Open Patent Publication (Tokkai) No. 2002-275786 discloses a method of using an additive comprising a fatty acid polyamidepolyamine. The paper obtained by this method has improved bulkiness, but foaming occurs in a higher degree during paper formation.
Furthermore, in all of the methods described above, paper dust tends to occur in the paper formation process or in the obtained paper.
In recent years, there is a demand for soft paper desired for comic books or paperbacks, and it is also desired to improve softness and touch for handy sanitary paper (e.g., bathroom tissue and facial tissue). Examples of softening agents to improve the softness of paper include glycerin, polyethylene glycol, urea, paraffin emulsifier, and a quaternary ammonium salt. For example, Japanese Laid-Open Patent Publication (Tokkai) No.5-156596 discloses a moisture absorbent for paper containing salts, polyhydric alcohols, or saccharides having hygroscopicity; Japanese Laid-Open Patent Publication (Tokkai) No.60-139897 discloses a softening agent for paper that is a fatty acid ester additive comprising oleic acid polyethylene glycol ester and dioleoyl phthalate; and Jaspanese Laid-Open Patent Publication (Tokuhyo) No.9-506683 discloses a softening agent for paper employing a polyhydroxyfatty acid amide compound. However, with these additives, a sufficient effect of improving the softness cannot be obtained and the foaming in the paper formation process is not suppressed.
When paper is produced by the use of pulp containing a large amount of waste paper pulp, much loading material such as fine fibers or calcium carbonate is contained in a pulp slurry of the system, so that the drainage of the pulp slurry is reduced. A method of adding a polymer compound such as polyacrylamide, polyethyleneimine in order to improve the drainage is known. However, when any of the above-described additives for providing bulky paper and such a polymer compound are used together in a paper formation system, the bulkiness effect of the additive is reduced. In the paper formation process, it is also desired to incorporate a large amount of fine fibers and loading material that are contained in the slurry into the paper (i.e., high retention is desired).
As described above, an additive for paper that can provide bulky and soft paper having a sufficient strength, that hardly causes foaming in the paper formation process, that provides a high retention and good drainage, and that causes no reduction in operability due to occurrence of paper dust has not been obtained yet.